Moles and Avogadro's Numbers

The atomic mass of helium is four grams per mole.

Number of moles is inversely proportional to molar mass.

Percentage yield = (0.45 ÷ 0.75) × 100 = 60%.

The balanced equation is 3Fe + 4H₂O → Fe₃O₄ + 4H₂. Their sum is 12.

Avogadro's law relates gas volume directly with the number of molecules at constant temperature and pressure.

The sample contains 0.25 mole of CO₂. Since one mole weighs 44 g, the mass is 11 g.

Half a mole of CO₂ occupies 11.2 dm³ at STP.

The molar mass divided by Avogadro's number gives the mass of one molecule.

Sixty-four grams of SO₂ equal one mole, producing one mole of SO₃.

One atomic mass unit is defined as one-twelfth the mass of a carbon-12 atom.

Actual yield equals 80% of theoretical yield. Therefore, 0.80 × 5 = 4 moles.

One methane molecule contains ten protons. Thus, one mole contains 10 × Avogadro's number of protons.

The balanced equation directly provides the ratio.

One mole always contains 6.022 × 10²³ elementary particles.

One mole of nitrogen produces two moles of nitrogen dioxide. Therefore, 0.5 mole yields one mole.

One mole occupies 22.4 dm³ at STP, so two moles occupy 44.8 dm³.

Forty-eight grams of magnesium equal two moles, producing two moles of MgO. The mass becomes 80 g.

Each NH₃ molecule contains three hydrogen atoms; therefore one mole of NH₃ contains three moles of hydrogen atoms.

Half a mole contains half of Avogadro's number of molecules.